Question

Write the formulas of the conjugate acids of the following Brønsted-Lowry bases: (a) \(\mathrm{ClCH}_{2} \mathrm{CO}_{2}^{-}\) (b) \(\mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N}\) (c) \(\mathrm{SeO}_{4}^{2-}\) (d) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{~N}\)

Short answer

(a) ClCH₂COOH (b) C₅H₅NH⁺ (c) HSeO₄⁻ (d) (CH₃)₃NH⁺

Step-by-step solution

Understanding Conjugate Acids

To find the conjugate acid of a Brønsted-Lowry base, we need to add a proton (H⁺) to the base. The addition of a proton converts the base into its conjugate acid form.

Find the Conjugate Acid of ClCH₂CO₂⁻

For the base \( \mathrm{ClCH}_{2} \mathrm{CO}_{2}^{-} \), add a proton \( \left( \mathrm{H}^{+} \right) \). This results in \( \mathrm{ClCH}_{2} \mathrm{CO}_{2H} \), also known as \( \mathrm{ClCH}_{2} \mathrm{COOH} \).

Find the Conjugate Acid of C₅H₅N

For the base \( \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N} \), add a proton \( \left( \mathrm{H}^{+} \right) \). This results in \( \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+} \).

Find the Conjugate Acid of SeO₄²⁻

For the base \( \mathrm{SeO}_{4}^{2-} \), add a proton \( \left( \mathrm{H}^{+} \right) \). This results in \( \mathrm{HSeO}_{4}^{-} \).

Find the Conjugate Acid of (CH₃)₃N

For the base \( \left( \mathrm{CH}_{3} \right)_{3} \mathrm{~N} \), add a proton \( \left( \mathrm{H}^{+} \right) \). This results in \( \left( \mathrm{CH}_{3} \right)_{3} \mathrm{NH}^{+} \).

Key concepts

Conjugate Acid

A conjugate acid forms when a Brønsted-Lowry base gains a proton. This process transforms the base molecule into a new species, the conjugate acid. Simply speaking, when a base accepts a hydrogen ion (ul>

It results in a new chemical entity.

The formula changes to include one more hydrogen atom.

A positive charge may appear due to the gained proton.

For example, if we start with the base \( \mathrm{ClCH}_{2} \mathrm{CO}_{2}^{-} \), adding a proton gives us \( \mathrm{ClCH}_{2} \mathrm{COOH} \), indicating this process.Being able to identify the conjugate acid allows us to understand how substances can act as buffers or participate in various chemical processes.

Protonation

Protonation refers to the process where a proton (H\(^{+}\)) is added to a molecule. It is a key step in forming conjugate acids from bases. The gain of this proton changes the base to its conjugate acid.

• This simple addition is crucial in many acid-base reactions.
• Understanding protonation provides insight into the reactivity of compounds.

Let’s take the base \( \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{~N} \) as an example. Through protonation, a proton is added, resulting in \( \mathrm{C}_{5} \mathrm{H}_{5} \mathrm{NH}^{+} \). This reveals not only the transforming effect a proton can have but also the dynamic nature of chemical reactions.

Chemical Formulas

Chemical formulas represent the composition of molecules. They show the elements involved and their quantities. In the context of finding conjugate acids, chemical formulas help us understand the molecular changes during protonation.

• Changes in chemical formulas can signal protonation.
• Notation like +(an additional element or charge) denotes new elements or charges added.

Consider the base \( \mathrm{SeO}_{4}^{2-} \). Ionically, this base gains a proton, becoming \( \mathrm{HSeO}_{4}^{-} \). Understanding the chemical formulas is key to grasping how compounds react and transform.

Step-by-Step Solution

A step-by-step solution involves breaking down complex processes into simpler, manageable parts. This approach helps tackle chemical exercises, like determining conjugate acids, more effectively.

• It allows a structured way to solve chemical problems.
• Encourages working through problems methodically.

For example, if we have a base like \( (\mathrm{CH}_{3})_{3} \mathrm{~N} \), the steps are: 1. Identify the base. 2. Add a proton. 3. Write the new formula: \( (\mathrm{CH}_{3})_{3} \mathrm{NH}^{+} \). This helps in tracking changes and understanding the chemical behavior. Through these steps, questions become more approachable and solvable.